The invention relates to a technique for using a hand-held device for forcing high pressure air into the ground around plant roots, loosening the soil and producing crevices therein, forcing granular fertilizer, pesticides, chemicals or the like into the crevices, and using the same device to force water into the crevices to dissolve the fertilizer or chemicals.
It is known that forcing substantial quantities of compressed air into the ground around the roots of trees and large shrubs can be beneficial, by loosening the soil, allowing escape of toxic materials that may be in the soil, and especially by facilitating injection of beneficial materials such as fertilizers and chemicals close to the plant roots. The same benefits have been recognized for broad scale application in commercial agricultural applications. U.S. Pat. No. 2,083,153 is perhaps the closest prior art. This device discloses an apparatus for injecting pressurized air into a pre-drilled hole to produce fissures in the deep soil. Soil-rectifying agents such as fertilizer and insecticide can be forced through the same tube through which the air passes into the fissures of the loosened soil. U.S. Pat. No. 4,429,647 discloses an apparatus connected to a high pressure air source and to a liquid fertilizer tank, for use in commercial agriculture. A system is described wherein a number of probes mounted on a tractor are forced by hydraulic means to a certain depth in the ground, wherein high pressure air then is forced through the probe in the soil, causing breaking up of the soil. Liquid fertilizer then is forced into the voids and cracks produced in the soil by the compressed air. The device described in U.S. Pat. No. 4,429,647 is not practical for use in private and commercial horticultural applications, as substantial force must be applied by a large machine to force the probes into the ground and to hold the probes in the ground when the high pressure air is applied. Small, hand-held devices that can be fit into small spaces and rapidly and easily deployed would be required for such private and commercial horticultural applications. Several hand-held devices for aerating soil around the roots of trees and shrubs are disclosed in U.S. Pat. Nos. 1,814,445 and 1,755,445. The latter patent discloses use of compressed air forced through a tube into the ground to first open up crevices around the roots by means of compressed air, and then diverts the compressed air into a fertilizer tank, forcing the fertilizer through the same tube into the ground to fill up the crevices. No such device has been widely used, however, probably because of the difficulty that an ordinary worker would experience in using it. If enough air pressure is applied to be effective in breaking up tightly packed, hardened soil around the roots of trees and shrubs, it would be difficult for most workers to keep the device in the ground and prevent most of the compressed air from flowing out in the atmosphere through the top of the hole into which the device is inserted, rather than being forced into the ground at the bottom of the hole and thereby loosening the soil.
A variety of devices that are insertable into the ground for providing controlled irrigation of plant roots and injection of chemicals and fertilizer are known, as indicated in U.S. Pat. Nos. 4,432,291, 3,916,564, and 3,900,962.
Despite the fairly widespread recognition that there can be advantages to using compressed air to loosen dirt around the roots of trees and shrubs, and that there can be advantages of conducting fertilizing and water through inserted tubes to locations fairly deep in the ground near the roots of plants, no one has yet provided an inexpensive, effective, hand-held device that can easily, economically, and rapidly improve the growth and appearance of trees and shrubs. There remains an unmet need for such a device.